This invention relates to a floating type magnetic head, and more particularly to a monolithic type magnetic head which is used for data recording/reproducing of mainly hard disks.
A floating type magnetic head of this type is generally provided with two or three rail like projections in the traveling direction of a disk on a core base member which faces a magnetic disk, and a magnetic gap is formed on the tip end of one of the projections. FIG. 4 is a perspective view to show a floating type magnetic head having three rail like projections viewed from the side contacting the disk wherein a base core 10 of a ferrite magnetic material is integrally formed with two separated grooves and three projected rails 11, 12, 13, and a front core 14 shaped like is attached to the front end of the central projection rail 12 to form a magnetic gap 15 therebetween.
FIG. 5 shows a magnetic head having two projected rails 11, 13 one of which 11 is attached to a front core 14 shaped like at the front end thereof. In either case, the front core 14 has a window 16 formed in the bored portion of the shape thereof and a winding 17 is wound around it. The projected rails are forced upon disk surface with a predetermined pressure by a spring (not shown) mounted between an attachment groove on the surface of the base core 10 and a head holder (not shown). The magnetic head as a whole becomes slightly floated from the disk due to the air resistance caused between the rails and disk when the magnetic disk is revolved. A magnetic gap 15 is then formed at the center of the width on the rail on the side facing the disk, and the length l thereof determines the width of a track which is being recorded on the magnetic disk.
As shown in FIG. 5, the portion where the rail front end is joined with the core 14 on the base core 10 is notched on both sides in a concave fashion and fused glass 18 is filled therein, forming a magnetic gap 15 at the center of the portion sandwiched by the glass-filled sides 18.
In most of the aforementioned prior art floating type magnetic heads, the front core and the magnetic gap thereof are formed on the center rail of the plural projected rails on a base core, and therefore when data is recorded by such a magnetic head on a magnetic disk and if the magnetic head is positioned at the outermost periphery of the disk, there is created a region between the outside rail 11 and the center rail 12 where recording tracks cannot be formed. At the inmost side of the disk, tracks cannot be formed also in the region extending from the position inside of the center rail 12 to the inner rail 13 to thereby reduce the recording capacity. Generally, the outermost track has a longer recording wavelength (recording interval along the track) and a larger output than inner tracks. Therefore, when a magnetic gap is formed at the central position of the base core as in the prior art, it is quite disadvantageous in terms of recording capacity. Even if a magnetic gap is formed on the outer rail as shown in the two-rail type device in FIG. 5, the position of the magnetic gap is closer to the inside on the rail surface facing the disk, or in other words at a position deviated from the outermost side of the rail inward by about 0.3 mm, the recording/reproducing region would be wasted by the width equal to deviation. The prior art magnetic head is also defective in that it needs a cumbersome process in manufacture as the rail has to be notched on both sides thereof and filled with fused glass subsequently.